Cranial Nerves: Sensory vs Motor
Cranial Nerves: Sensory vs Motor
Cranial nerves are essential for various functions and are classified based on their modality: either sensory, motor, or both. Each cranial nerve has a specific function and travels through particular foramina in the skull. Below is a detailed description of each cranial nerve, their nuclei, levels, foramina, mode (sensory, motor, or both), functions, ganglia, and reflexes.
I: Olfactory Nerve
- Foramina: Cribriform plate
- Mode: Sensory
- Function: Sense of smell
- Ganglion/Reflex: None
II: Optic Nerve
- Foramina: Optic canal
- Mode: Sensory
- Function: Vision
- Ganglion/Reflex: Pupillary light
III: Oculomotor Nerve
- Nucleus Level: Midbrain
- Foramina: Superior orbital fissure
- Mode: Motor
- Functions:
- Motor to levator palpebrae superioris and all extraocular eye muscles except superior oblique and lateral rectus
- Parasympathetic supply to ciliary muscle and constrictor pupillae
- Ganglion/Reflex: Ciliary, Pupillary light, Accommodation, VOR
IV: Trochlear Nerve
- Nucleus Level: Midbrain
- Foramina: Superior orbital fissure
- Mode: Motor
- Function: Motor to superior oblique muscle
- Ganglion/Reflex: None
V: Trigeminal Nerve
- Nucleus Level: Pons
- Foramina: Superior orbital fissure; Foramen rotundum; Foramen ovale
- Mode: Both Sensory and Motor
- Functions:
- Sensory from skin and mucous membranes of head: sclera, sinuses, nasal cavities, meninges, tympanic membrane (external surface), TMJ, teeth and gingivae, anterior 2/3 tongue and oral cavity
- Motor to muscles of mastication, mylohyoid, anterior belly of digastric, tensor veli palatine, and tensor tympani
- Sensory from skin and mucous membranes of head: sclera, sinuses, nasal cavities, meninges, tympanic membrane (external surface), TMJ, teeth and gingivae, anterior 2/3 tongue and oral cavity
- Ganglion/Reflex: Trigeminal, Corneal blink, Sneeze, Jaw jerk
VI: Abducens Nerve
- Nucleus Level: Pons
- Foramina: Superior orbital fissure
- Mode: Motor
- Function: Motor to lateral rectus muscle
- Ganglion/Reflex: VOR
VII: Facial Nerve
- Nucleus Level: Pons
- Foramina: Internal Acoustic Meatus; Stylomastoid Foramen
- Mode: Both Sensory and Motor
- Functions:
- Sensation from part of the external ear, external surface of the tympanic membrane, and palate
- Taste anterior 2/3 of tongue and palate
- Parasympathetic supply to lacrimal, nasal, submandibular, and sublingual glands
- Motor to muscles of facial expression, posterior belly of digastric, stylohyoid, and stapedius
- Ganglion/Reflex: Geniculate, Pterygopalatine, Submandibular, Corneal blink
VIII: Vestibulocochlear Nerve
- Nucleus Level: Pons/Medulla
- Foramina: Internal Acoustic Meatus
- Mode: Sensory
- Functions:
- Balance (Vestibular)
- Hearing (Spiral)
- Balance (Vestibular)
- Ganglion/Reflex: Vestibular (VOR, nystagmus), Spiral
IX: Glossopharyngeal Nerve
- Nucleus Level: Medulla
- Foramina: Jugular foramen
- Mode: Both Sensory and Motor
- Functions:
- Sensation from external ear, posterior 1/3 of tongue, internal surface of tympanic membrane, oropharynx, visceral sensory from the carotid body & sinus
- Taste for posterior 1/3 of tongue
- Motor to stylopharyngeus muscle
- Parasympathetic to parotid gland
- Ganglion/Reflex: Superior, Inferior, Otic, Gag
X: Vagus Nerve
- Nucleus Level: Medulla
- Foramina: Jugular foramen
- Mode: Both Sensory and Motor
- Functions:
- Sensation from part of the external ear, external acoustic meatus, epiglottis and base of tongue, laryngopharynx, larynx, viscera, and aorta
- Taste from the epiglottis and base of tongue
- Motor to muscles of pharynx, larynx, and palate (excluding stylopharyngeus and tensor veli palatine)
- Parasympathetic supply to thoracic and abdominal viscera
- Sensation from part of the external ear, external acoustic meatus, epiglottis and base of tongue, laryngopharynx, larynx, viscera, and aorta
- Ganglion/Reflex: Superior, Inferior, Sneeze, Gag, Cough
XI: Accessory Nerve
- Nucleus Level: Cervical Spinal Cord
- Foramina: Foramen Magnum; Jugular foramen
- Mode: Motor
- Function: Motor to sternocleidomastoid and trapezius muscles
- Ganglion/Reflex: None
XII: Hypoglossal Nerve
- Nucleus Level: Medulla
- Foramina: Hypoglossal foramen
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- Mode: Motor
- Function: Motor to intrinsic and extrinsic muscles of tongue (excluding palatoglossus)
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- Ganglion/Reflex: None
Sensory and Motor Modalities
- General Somatic Afferent (GSA): Sensory from the skin and membranes, e.g., cranial nerves V, VII, IX, X.
- General Visceral Afferent (GVA): Sensory from viscera and organs, e.g., cranial nerves IX, X.
- Special Sensory Afferent (SSA): Specialized senses like vision and hearing, e.g., cranial nerves II, VIII.
- General Somatic Efferent (GSE): Motor to skeletal muscles, e.g., cranial nerves III, IV, VI, XII.
- Special Visceral Afferent (SVA): Sensory related to taste and smell, e.g., cranial nerves I, VII, IX, X.
- Special Visceral Efferent (SVE): Motor to muscles derived from branchial arches, e.g., cranial nerves V, VII, IX, X, XI.
- General Visceral Efferent (GVE): Motor to visceral organs and parasympathetic supply, e.g., cranial nerves III, VII, IX, X.